Process of obtaining zinc oxid from zinc ores.



No. 875,866. PATENTED JAN. 7, 1908.

- H. L. SULMAN. v PROCESS OF OBTAINING ZINC OXID FROMZING ORES.

APP'LIOATION FILED O0T.30. 1006.

I I N UNITED STATES PATENT OFFICE.

HENRY LIVINGSTONE SULMAN, OF LONDON, ENGLAND.

PROCESS OF OBTAINING ZINC OXID FROM ZINC ORES.

Specification of Letters Patent.

Patented Jan. '7, 1908.

Application filed October 30.1906. Serial No. 341.350,

.Process of Obtaining Zinc Oxid from Zinc Ores, of which the following is a specification.

This invention has for its object to obtain,

zinc oXid from zinc ores, compounds and products. Such ores or products may contain other metals besides zinc, such as lead, copper, silver, gold, etc, which upon the separation of the zinc are left in a state suitab e for recovery by other known methods, such as smelting, etc. Complex sulfid ores containing zinc, lead, silver, etc., the residuesi'rom the zinc distillation process, ferruginous zinc ores, and other ores or products of zinc are suitable for treatment by this method. The )I'OCBSS belongs to the known type in which zinc ore roasted if necessary to produce zinc oXid is treated with sulfurous acid to dissolve the zinc oxid.

According to this invention, in the separation of zinc from its ores, the zinc 18 0011- vertedlnto OXld, the product is treated with a solution of sulfurous acid so as to obtain a solution of bisulfite of zinc and the zinc is precipitated .as insoluble monosulfite by the addition of zinc oxid to the solution. For

example, in treating a mixed ore containing zinc sulfid, the process consists in roasting the ore to convert the zlnc into zinc OXld and yieldsulfurous acid, treating the productzinc is contained be a sulfid ore, or if the zinc exists in the state of blende, the ore is subjected to a'dead roast in order to obtain the Zinc as oxid, the other metals present being also transformed into-oXids, or in the case of lead mainly into sulfate. The roasted material is now treated with an excess of sulfurous acid in a suitable vessel in the presence of suflicient water to dissolve the bisulfite of zinc so produced. The vessel may be one through which furnace gases sufficiently rich in sulfurous acid may be passed, and means for gentle attrition of the ore with the sulfurous acid solution, or for suitable stirring, may be provided in order to facilitate the dissolution of the zinc oxid. The solution vessel would be connected with condensation towers or suitable plant for arresting and recovering any excess.of sulfurous acid for further operations. If the raw material carry zinc in the shape of oXid, or of readily decomposed silicate, or in the metallic condition, such preliminary roasting is not required, but the product can be at once treated with sulfurous acid and water for the purpose of dissolving the zinc mainly as bisufite. Fragments of metallic zinc of sensible size tend. to become coveredwith a layer of 'zinc sul'iid and to be only partially attacked; but such would be recovered from the undissolved residue by a subsequent vanning operation. i

If silver be present in the ore, a soluble chlorid, suchassalt, should be added to keep the silver insoluble, as silver chlorid', and thus render it available for recovery by smelting the zinc exhausted residue with lead in the ordinary way.

The zinc bisuliite solution is now filtered from the insoluble residue, upon any suitable filter surface, or in a filter-press, and the residue washed free from soluble zinc, the washings being added to the main solution. The residue is now treated for the extraction of the other values which it may contain aceording to known means which form no part of this invention; i. 6., if it "ontain a suitable quantity of lead it may be smelted by the usual processes, by which any silver and gold present in the residues will be recovered in the lead bullion obtained. Or if the de zincked material contain metallic lead, or other substances capable of separation in a water current, the product may be subjected to a vanning operation for the recovery of such metallic or mineral'values; such a method would be applicable to the product submitted to attrition in suitable apparatus,

such as a tube-mill or grit-mill, t at is to say, a cylinder or barrel rotatable on its axis and half filled with spherical stones or large. marbles, or subjected to other similar light and continuous grinding, this film or crust of nionosulfite. is constantly broken up, and fresh surfaces of'oxid exposed, with the resulting complete precipitation of the total zinc.

zinc present in the form of monosulfite of It is found moreover that by such means the monosulfite of zinc suspended in the pulp issuing from the mill is in a more or less granular and crystalline form and is capable of ready filtration. This precipitation of bisulfite of zinc by zinc oxid takes place readily in'the cold. The zinc monosufite is now filtered from the liquor which may be run to waste, the sulfite being collected, dried, and submitted to calcination whereby zinc oxid is produced which can then be dealt with for the manufacture of spelter in the ordinary way. A portion of this oxid of zinc is returned to the grit-millfor the precipitation of fresh bisulfite of zinc, so that a moiety of zinc oxid is always in use cyclically.

The sulfurous acid resulting from this calcination is collected, in the condr using tower or by suitable arrangements used for dissolv ing the further zinc oxid from roasted ores, or for the' solution of other forms of zinc as before described, so far as may be desirable or necessary.

This process is also suitable fordealin with the lead and zinc concentrates obtained by physical or mechanical separation processes, and for effecting a sharp separation of lead and silver, and of zinc, therefrom. It is not necessary to carry the precipitation of zinc bisulfite to completeness by means of zinc oxid; the last few percentages of soluble bisulfite may, if desired, be thrown down by lime as the proportion of calcium sulfate resulting is too small to affect the main bulk of the final oxid product disadvantageously, ifthis material is to be subjected to spelter distillation. Or the last traces may also be precipitated by a soluble alkaliin place of continued attrition with zinc oxid. Such final precipitation may be resorted to in the event of small quantities of sulfate of zinc being present in the solution.

It is to be understood that the details of.

the process may bevaried without departing from this'invention. v

In the drawing there is illustrated diagrammatically an apparatus for carrying out the process.

In said drawings A is a hopper through which the ore is fed into the muffle furnace B. The sulfur dioxid is led through the pipe (I to the condensing towers D. The roasted ore from the muffle furnace B is led through the conve'yer E to a hopper F which feeds the ore into a rotatable tube mill G. The sulfurous acid solution from the condensing towers D is also led into the tube mill G through a conduit H. The contents of the tube 'inill G are continuously discharged through the outlet J. on to a filter K.

solid residue in the filter is removed at L to be smelted or otherwise treated. The liquid filtrate from the filter K is led through the conduit M into the rotatable tube mill N and at the same time thezinc oxid is fed into the tubemill'N through the hopper O. The contents of the tube mill N are continuously discharged through the outlet P to the-filter Q. The liquid filtrate which generally consists simply of-water is discharged through outlet R to waste. The solid residue consisting of zinc monosulfite is led from the filter Q into a. hopper S which supplies themufile furnace T in whichthe zinc'monosuh fite is split up into zincoxid and sulfurous acid. The sulfurous acid is led through the conduit U into the tube mill G so that the sulfurous acid is used cyclically. The zinc oxid produced in the muffle furnace T is removed at V and one half of it is returned to the hopper O to be introduced into the tube mill N. In order that the Whole process may be a continuously operating one the furaces should be continuously operating.

The V What I claim as 'my' invention and desire sulfite, and calcining the monosulfite to produce zinc oxid.

3. The herein described process for obtaining zinc oxid from Zinc ores which consists in dissolving zinc oxid from the ore with sulfurous acid, adding zinc oxid to the bisulfite solution thus obtained to precipitatekthe insoluble monosulfite of zinc, submitting the mixture to attrition to prevent incrustation oxid which will precipitate the zinc as monoof the zinc oxid by zinc monosulfite, and cal- I cining the monosulfite to produce zincoxid.

4. The hereindescribed process for obtaining zinc oxid from zinc ores which consists in converting the zinc into oxid, treating the ore with sulfurous acid solution to dissolve the zincas bisulfite, separating thebisul'tite solution from the residue, adding to the solution zinc oxid which will remove sulturous acid and precipitate the zinc as monosul'lite, separating the zinc inonosuliite from the liquor and drying and calcining the same to produce zinc oxid.

5. The herein described process for obtaining zinc oXid from zinc ores which consists in converting the zinc into oxid, treating the ore with sulturous acid solution to dissolve the zinc as bisulfite, separating the bisuhite solution from the residue, adding to the solution zinc oxid which wil remove sulturous acid and precipitate the zinc as monosul'fite, separating the zinc monosuliite from the-liquor and drying and calcining the same to produce zinc oxid, and collecting the sulfurous acid evolved for repeated use.

6. The herein described process torobtaim ing zinc oxid from zinc ores which consists in roasting the ore to obta n the zinc as end, dissolving the Z1110 oxid from the ore with sulfurous acid, treating the resulting bisultite solution with zinc oxid to convert the soluble bisulfite of zinc into insoluble monosul'fite and calcining the monosulfite to produce zinc oXid.

7. The herein described process for obtaining zinc oXid from zinc ores which consists in roasting-the ore to obtain the-zinc as oxid, treating the roasted material with an excess of sulfurous acid in the presence of sufficient water to dissolve the 'bisul'tite or zinc so produced, filtering the bisulfite solution from the residue, treating the solution with oxid of zinc to convert the soluble bisul'iite of zinc into insoluble monosulhte by removal oi sult'urous acid, filtering the zinc monosultitc from the liquor and drying and calcining the same to produce zinc oxid.

The herein described process for obtaining zinc oxid from zinc ores which consists in roasting the ore to obtain the zinc as oxid, treating the roasted material with an excess of sulturous acid in the presence of sullicient water to dissolve the bisul'lite of zinc so produced, filtering the bisuliite solution from the/residue, treating the solution withox o'l' zine. to convert the soluble bisuliite ol' :4 into insoluble monosul'lite by removal of s. lurous acid, submitting the mixture to attrition to prevent iucrustation of the zinc oxid by monosul'lite, filtering the zinc monosuliite from the liquor, and drying and calcining the same to produce zinc oxid.

9. The herein described process for obtaining Zinc oxid'l'rom zinc ores which consists in roasting i ilv ire to obtain the zinc as oxid, treating the roasted material with an excess of sullurous acid in the presence of sullicient water to dissolve the bisul'tite of zinc so produced, filtering the bisuliite solution from the residue, treating the solution with oxid of zinc to convert the soluble bisulfite of zinc into insoluble monosulfite by removal of sull'urous acid, submitting the mixture to attrition to prevent incrustation of the zinc oxid by monosuliite,filtering the zinc monosuliitc l'rom the liquor, and drying and calcining the same to produce zinc oxid and collecting the sull'urous acid evolved for repeated use.

In testimony whereof I have signed my name to this specification in. the presence of. 

